Tidal Flats
Enchantment
: For each attacking creature without flying, its controller may pay 
. If that player doesn't, creatures you control blocking that creature gain first strike until end of turn.
Rob Alexander
Fallen Empires (FEM)
• #27aRulings
Can be used more than once in a turn. Each time, the opponent can pay to prevent giving first strike to a creature, but this payment only stops the current activation and not future activations of Tidal Flats.
(wotc • 2004-10-04)
First Strike is granted to your creatures currently blocking non-Flyers when this effect resolves.
(wotc • 2004-10-04)
The payment is made when the Tidal Flats effect resolves.
(wotc • 2004-10-04)
Rulings
Can be used more than once in a turn. Each time, the opponent can pay to prevent giving first strike to a creature, but this payment only stops the current activation and not future activations of Tidal Flats.
(wotc • 2004-10-04)
First Strike is granted to your creatures currently blocking non-Flyers when this effect resolves.
(wotc • 2004-10-04)
The payment is made when the Tidal Flats effect resolves.
(wotc • 2004-10-04)